Were these three cultures aware of each others existence? Did they trade with one another?
Aztecs did know about Mayas but the Mayan civilization was already dead. But of course, they did traded with its descendants - even prehistoric men traded with their neighbours.
And no direct contacts for the contemporary Incas civilization.
The only question remains open - if Incas knew about Mayas
This article on Pre-Columbian Trade by Chester S. Chard would suggest they did. For instance:
There is no evidence that Maya traders themselves reached the highlands of Mexico; they traded their goods in the great commercial center of Xicalango, whence others carried them on. It is reported that the merchants of Xicalango furnished Cortez with fairly correct maps of the entire region to the south as far as Panama, which suggests extensive trade contacts.
There's a map on p.2 that shows established, sporadic, conjectured trade routes. I've only skimmed a few passages, but it seems pretty clear the Mayans were aware of and de facto trading with the other two. At the very least one could suggest it may have been like the Romans, who knew the Chinese existed and de facto traded with them through intermediaries.
Anecdotally I recollect also reading somewhere (possibly on this site or in a source reference from it) that the Spaniards' reputation had reached Florida long before they actually showed up, resulting in fairly hostile natives.
The Aztecs and the Mayas did know about each other. After all, they were right next to each other. But I don't think there is any evidence that one of those two civilizations met the Incas. Probably since the Incas were pretty far away.
Although I think that if there had been contact, the Mayas would've had the biggest chance since they traded more.